Frogun Perilous Aqueduct Obsidian Skull Location

gamespot.com:

Every level of Frogun is absolutely teeming with collectibles to grab if you want to get full completion. While you're rounding up all of the coins, gems, and pages, you'll need to keep an eye out for each stage's Obsidian Skull, which usually requires you to find a secret entrance (a huge hole in the ground). One early level called Perilous Aqueduct has a surprisingly well-hidden secret entrance that can be overlooked very easily if you're not paying close attention. But no worries--in this guide, we'll tell you where to find the secret entrance and claim the Perilous Aqueduct Obsidian Skull for yourself.

When the level begins, simply play through the opening section until you come across the first bouncy mushroom. Use it, then cross over the area with the rolling boulders. Instead of continuing full down the stairs ahead, however, stop and note a hidden path to the left that takes you behind the waterfall.

Make your way up the platforms until you reach the top of the waterfall. At one end of the narrow ledge is a slow-moving and easy-to-miss floating platform that can ferry you across the sky to a hole, which teleports you to the challenge area where you'll find the Obsidian Skull.

Once you've fallen in the hole, you'll see the Obsidian Skull just on the other side of a handful of lily pads. Now that you've found where it's hiding, snagging it shouldn't be too much of a challenge. Once you grab it, you can exit back out the other hole and find yourself back in the base level ready to continue your journey through the Perilous Aqueduct.